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Petrology of the neoproterozoic, exo-granitic Kuiperskraal Sn-Zn-As deposit, Western Cape Province, South Africa
Thesis (M.Sc.) -- University of Stellenbosch, 1998.
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| Format: | Thesis |
| Language: | en_ZA |
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Stellenbosch : Stellenbosch University
2012
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| _version_ | 1867613740827934720 |
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| access_status_str | Open Access |
| author | Bruwer, Louise |
| author2 | Rozendaal, A. |
| author_browse | Bruwer, Louise Rozendaal, A. |
| author_facet | Rozendaal, A. Bruwer, Louise |
| author_sort | Bruwer, Louise |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Thesis (M.Sc.) -- University of Stellenbosch, 1998. |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/55950 |
| institution | Stellenbosch University (South Africa) |
| language | en_ZA |
| last_indexed | 2026-06-10T12:40:57.522Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2012 |
| publishDateRange | 2012 |
| publishDateSort | 2012 |
| publisher | Stellenbosch : Stellenbosch University |
| publisherStr | Stellenbosch : Stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/55950 Petrology of the neoproterozoic, exo-granitic Kuiperskraal Sn-Zn-As deposit, Western Cape Province, South Africa Bruwer, Louise Rozendaal, A. Stellenbosch University. Faculty of Science. Dept. of Earth Sciences. Petrology -- South Africa -- Western Cape Geology, Stratigraphic -- Proterozoic Dissertations -- Geology Thesis (M.Sc.) -- University of Stellenbosch, 1998. The Kuiperskraal Sn-Zn-As deposit is • situated in the Kuiperskraal-DorstbergKanonkop (KOK) area, near Bellville in the Western Cape Province, South Africa. This study was initiated to determine the nature of the hydrothermal fluids responsible for the Sn-Zn-As mineralization and to ascertain whether the fluid system was capable of transporting and depositing gold. Mineralogy, geochemistry (both whole rock and mineral), fluid inclusion and isotope studies were conducted to draw a conclusion. The KOK area is underlain by Malmesbury Group metasediments and metavolcanics, which were deposited in an early retro-arc continental margin basin. The tectono-stratigraphic Tygerberg terrane forms the southwestern portion of the Malmesbury Group and comprises predominantly greywacke and pelites in the KOK area. Multiphase deformation of these sedimentary rocks occurred during the Saldania orogeny (650-580 Ma), subjecting the metasediment to regional metamorphism. Syn- and post-tectonic S-type granitoids (600-540 Ma) intruded the Malmesbury rocks in the Tygerberg terrane. Intrusion of the granitoids resulted in contact metamorphic aureoles and the formation of cordierite hornfels. A variant of the S-type granitoids in the Tygerberg terrane, the peraluminous Sa2-subtype, locally known as the Kanonkop granite, intruded at a later stage. Late magmatic hydrothermal fluids cause greisenization of cupolas of the granite bodies in the Tygerberg terrane and associated endo-granitic Sn-W mineralization. Exe-granitic veins, of which some are mineralized, are localized in structural traps such as fold hinges, producing manta-type deposits. Five exo-granitic vein types are identified in the KOK area, namely quartz±mica±tourmaline, quartz - cassiterite - arsenopyrite - sphalerite - tourmaline, quartz - chlorite - actinolite ± clinopyroxene, quartz - chlorite - calcite - actinolite, and carbonatized veins. The first generation of high temperature veins was formed by hydrothermal fluids with a pressure-corrected temperature of 400-550°C. During this phase, cassiterite and tourmaline were the first to crystallize followed by the sulphides at a decrease in temperature to produce quartz - cassiterite - arsenopyrite - sphalerite - tourmaline veins. Subsequent lower temperature fluids (250-300°C) produced quartz - chlorite - calcite - actinolite and quartz - calcite - actinolite ± clinopyroxene veins, with clinopyroxene and quartz the first to crystallize. Carbonates in veins crystallized at temperatures ranging from 150°C to 190°C. Isotope data indicate very limited mixing of the magmatic fluids with meteoric water. The magmatically derived hydrothermal fluids responsible for the formation of the exo-granitic veins in the KOK area are enriched in metals (Sn, Zn, As) and volatiles (8, Cl, OH-, CO2, F) and are slightly alkaline. The hydrothermal fluids responsible for the various veins (mineralized or unmineralized) in the KOK area extracted iron, magnesium, aluminium and calcium from the wall rocks to produced intensive wall rock alteration zones. The mineral composition of the alteration zones is related to the mineral composition of the veins. Intensive tourmalinization of the wall rocks accompanied the quartz-cassiteritearsenopyrite-sphalerite-tourmaline veins. However, the wall rocks surrounding quartz-chlorite-calcite-actinolite, quartz-calcite-actinolite±clinopyroxene and retrogressive carbonatized veins are retrogressively altered to a quartz, chlorite, calcite and actinolite composition. The ferromagnesian minerals active in the hydrothermal system underwent a change from Fe-riched endo-granite to Mgenriched exo-granitic, as a function of the host rock chemistry. Distal manta mineralization and the associated lower hydrothermal fluid temperature are characterized by Sn, Zn and abundant sulphide mineralization. The lower temperature explains the absence of tungsten in the veins. The fact that gold concentrations are normally unlikely in these deposits, despite the high concentrations of arsenic (1 1 % As), is corroborated by the absence of the element in all the analyses, despite it being reported in the literature. Considerable potential for similar subsurface deposits, particularly in structural traps, exists in the Kuiperskraal and surrounding areas. The peraluminous Sa2 granitic event seems to have a low gold potential. Masters 2012-08-27T11:37:18Z 2012-08-27T11:37:18Z 1998 Thesis http://hdl.handle.net/10019.1/55950 en_ZA Stellenbosch University 211 pages : ill. application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Petrology -- South Africa -- Western Cape Geology, Stratigraphic -- Proterozoic Dissertations -- Geology Bruwer, Louise Petrology of the neoproterozoic, exo-granitic Kuiperskraal Sn-Zn-As deposit, Western Cape Province, South Africa |
| title | Petrology of the neoproterozoic, exo-granitic Kuiperskraal Sn-Zn-As deposit, Western Cape Province, South Africa |
| title_full | Petrology of the neoproterozoic, exo-granitic Kuiperskraal Sn-Zn-As deposit, Western Cape Province, South Africa |
| title_fullStr | Petrology of the neoproterozoic, exo-granitic Kuiperskraal Sn-Zn-As deposit, Western Cape Province, South Africa |
| title_full_unstemmed | Petrology of the neoproterozoic, exo-granitic Kuiperskraal Sn-Zn-As deposit, Western Cape Province, South Africa |
| title_short | Petrology of the neoproterozoic, exo-granitic Kuiperskraal Sn-Zn-As deposit, Western Cape Province, South Africa |
| title_sort | petrology of the neoproterozoic exo granitic kuiperskraal sn zn as deposit western cape province south africa |
| topic | Petrology -- South Africa -- Western Cape Geology, Stratigraphic -- Proterozoic Dissertations -- Geology |
| url | http://hdl.handle.net/10019.1/55950 |
| work_keys_str_mv | AT bruwerlouise petrologyoftheneoproterozoicexogranitickuiperskraalsnznasdepositwesterncapeprovincesouthafrica |